My knees are weak through fasting; and my flesh lacks fatness.
Read Chapter 109
Augustine of Hippo
24. "I became also a reproach unto them" (ver. 24): through the death of the Cross. "For Christ hath redeemed us from the curse of the law, being made a curse for us." "They looked upon Me, and shaked their heads." Because they beheld His crucifixion, without beholding His resurrection: they saw when His knees were weakened, they saw not when His flesh was changed.
Heads, and saying, Vah (Matthew xxvii. 40.) as Semei insulted David, (2 Kings xvi. 5.; Calmet) though he is not said to have shaken his head, for which reason the prophecy may rather relate solely to Christ. (Berthier)
"To pay our ransom, he was crucified; to be crucified, he was despised; and to be despised, he appeared in a state of abjection. "(St. Augustine)
These three steps were requisite, as the Jews would never have dared to lay hands on him, if he had appeared in glory. (Berthier)